In electronics and electrical engineering, there are known a large number of electromechanical connections, which serve to transmit electrical currents, electrical voltages and/or electrical signals with the greatest possible range of currents, voltages, frequencies and/or data rates. Such connections must temporarily or permanently ensure correct transmission of mechanical contact, electrical power electrical signals and/or data under thermally loaded, dirty, damp and/or chemically aggressive conditions. Therefore, a large number of specially constructed electromechanical contacts, in particular crimp contacts are known.
A crimp connection is a solderless connection. The shape of the crimp and amount of pressure applied must be correct in order to obtain desired performance and durability of the connection. Improper crimps may generate heat due to poor electrical connection and may result in the rework of the product, increased scrap, and in extreme cases catastrophic failure.
Electrical terminals are often used to terminate the ends of wires. Such electrical terminals typically include an electrical contact and a crimp barrel. In some terminals, the crimp barrel includes an open area that receives an end of the wire therein. The crimp barrel is crimped around the end of the wire to establish an electrical connection between electrical conductors in the wire and the terminal as well as to mechanically hold the electrical terminal on the wire end. When crimped over the wire end, the crimp barrel establishes an electrical and mechanical connection between the conductors of the wire and the electrical contact. In addition to a permanent electrical connection, a permanent mechanical connection must also be produced between the cable and a conductor crimp region of the crimp contact. For an electromechanical connection, the crimp contact has the conductor crimp region and in most cases an insulation crimp region for the cable. Miniaturization and cost savings are forcing manufacturers towards smaller and thinner contacts.
Crimp connections known in the art serve to establish an electrical contact as well as to provide a mechanically resilient connection between a crimping base and at least one electrical conductor, which can consist of one or more individual wires. The crimp barrel usually consists of a metal plate, which is bent to have a U- or V-shaped cross-section or has rectangular cross-section with a flat base. The underside of the U- or V-shape is referred to as a crimp base. The upwardly pointing legs of the U- or V-shape are generally known as crimp flanks.
The crimp connection is produced by a crimping die, which consists of an anvil and a crimping stamp. For crimping, the crimping base is positioned centrally on the anvil, and the electrical conductor is placed between crimping legs on the crimping barrel. Subsequently, the crimping stamp descends onto the anvil and bends the crimp flanks around the electrical conductor in order to compress it tightly and to fix it in a force-locking manner with the crimping barrel. In the transition area from the crimp base to the crimp side walls, the so-called crimping roots, as well as laterally at the crimp side walls, zones of high bending stresses are formed in the crimp barrel. The force connection between the crimp barrel and the electrical conductor can be improved by providing additional form-fitting elements for example, recesses or depressions on the inner side of the crimp barrel facing the conductor for the creation of locking elements, wherein displaced conductor material can penetrate into the recesses during compression. The pressed zones of a crimping connection may have better electrical properties and the less heavily pressed areas have a higher mechanical stability. The crimping barrel and the electrical conductor can be locally reinforced by steps or projections in the crimping die.
U.S. Pat. No. 5,901,439 discloses how the compression of a crimp can be locally increased by feeding an additional punch through an opening in the working surface of the anvil when the crimping die is closed.
If the crimp connection is subjected to mechanical stress, the crimping flanks may spring up along the crimping roots and other zones of high bending stresses. There is the risk that the crimping base opens along the longitudinal seam at the ends of the crimp side walls. Depending on the type of stress, the ends of the crimp side walls can also move axially relative to each other. A reduction in the crimping forces, however, can result in the individual wires of the electrical conductor moving relative to each other. When they are displaced in the longitudinal direction, the force of the crimped connection is reduced by the resultant free spaces. The free spaces offer the possibility of external material penetrating into the crimped connection. The crimping forces are then further weakened by corrosion of the electrical conductor and the crimping barrel caused by the external agents.
In the event of a loss of crimping force, the desired mechanical stability of the crimping connection can no longer be maintained. It was found that in case of movements on the connected line or the electrical conductor, a movement of the individual wires of the electrical conductor at the other end of the crimp connection can be observed. This indicates that both the individual wires of the electrical conductor, as well as the electrical conductor and the crimp barrel are no longer fixed in a sufficiently secure manner. In the individual case, therefore, increased electrical transition resistances between the crimp barrel and the electrical conductor can occur.
To achieve mechanical and electrical robustness of the crimp connection, the crimp barrel must have sufficient stock thickness of the sheet metal related to the wire size. Especially for large wire sizes, this minimum barrel stock thickness creates disadvantages as it presents difficulty in cutting, bending, or forming in the stamping process to manufacture an electrical element from sheet metal, and requires high force for crimping and requires high material costs.
On the other hand, when using too thin stock, the crimp starts to fail at the seam of the roll-in for mechanical and electrical performance. German Patent Application DE 102006045567 describes a staggered seam on an F-Crimp formed by a crimp tool with consecutive offset in the roll-in geometry. In this crimp connection, the crimp with a thinner sheet metal presents the problems mentioned above.
The measures known in the art for providing form-locking elements or a reinforced crimping connection elements cannot prevent the crimp barrel from being deflected and permit a relative movement of the individual wires of the electrical conductor and the resulting losses of crimping forces.